Spark plug



Feb. 14, 1928. 1,659,037-

M. F. MACDONALD SPARK PLUG Filed March 1925 INVENTOR Ma L nard f. Macdonald I ATTORNEYS Patented Feb. 14, 1928.

UNITED STATES MAYNARD F. MACDONALD, OF VICTORIA, BRITISH COLUMBIA, CANADA, ASSIGNOR TO JUPITER SPARK PLUG- COMPANY, 01E SEATTLE, WASHINGTON, A CORPORATION OF 1 WASHINGTON.

SPARK PLUG.

Application filed March 31, 1925 Serial No. 19,610.

My invention relates to spark plugs and particularly to plugs of the general type shown in my Patent No. 1,513,057, issued October 28, 1924s I have found in connection with plugs of this type; employing a ball-ended or other wise enlarged electrode cooperating directly with the apron depending from the lower end of the shell, that instead of firing about the entire circumference of the ball the spark tends to jump at one or two places, hence his not important that the ball be employed to induce a multiplicity of sparks; but I have found that the ball is chiefly desirable for the directional effect it has on thev gases passing through or past the spark gap and out of the ports in the apron. I have found, too, that the discharge from the circumference of a ball-ended electrode to the rim or end of the apron has a tendency to be weak and ineffectual, hence it is desirable to concentrate the spark. It is the I chief object of the present invention, there fore, to retain the advantages of my former plug in that it prevents fouling through the action of a draft of gases past the spark gap and over the end of the insulator, and .having the additional advantage of a hot, concentrated spark. v

A further object is so to position two complemental electrodes in a plug of this character, that they will best cooperate with each other to produce a hot, fat spark.

The means by which these objects are attained are shown ina number of forms in the accompanying drawings, wherein:

Figure 1 is an axial section through one form of plug;

form;

Figure 3 is a side elevation with parts broken away of a modified form;

Figures 4L- and 5 are, respectively, a side elevation with parts broken away, and an underside view, of another modification;

Figureo is a side elevation, with parts broken away, of another modification.

In general my invention is similar in form and in principle of operation to my previous invention. As shown, a porcelain. insulator 1 has extending through it a positive electrode 2, the porcelain projecting from its seat at 31 within an externally threaded edges of the ports 33.

Figure 2is an underside view of the same shell 3, and being held therein by a gland ing ports 33 therethrough positioned above the lower end of the electrode 2 and preferably being outwardly flared, at their upper edges at least, as indicatedat 34.

Referring to Figures 1 and 2, it will be seen that the electrode 2 has a ball 22 formed upon its lower end, and preferably positioned at aboutthe lower end of the apron 32, or at least well below the upper The ball is not large enough to cooperate with the apron 32 to form a spark gap thereb-etween, but the electrod-e2 may have a tip 21 extending slightly below the ball, and a negative electrode 35 secured in the apron extends toward and cooperates with the tip 21 to form a spark gap 23 therebetween. Thus the ball serves to part or deflect the gases as they are forced upward, and to direct them upwardly and outwardly uniformly in all directions, and through the ports 33, the flared walls 34 of these ports assisting in thus directing the gases in a smoothly curved path, as is indi' c'ated by the arrow A in Figure 1, and in fact, by its outrush' through these flared ports, creating a suction in all parts of the chamber 25 within the shell. The ball being of small diameter, thespark gap is thus substantially in the direct line of these gases, and, as in my former invention, they serve to keep the sparking points clear and free of oil or carbon-deposits;

A further function of a deflector at the lower end of the electrode 2, typified by the ball 22, is the direct protection of the end of the insulatonl from carbon which would tend to'accumulate thereon, and which would eventually shortcir'cuit the plug by forming a connection between the electrode 2 and the shell 3, and the indirect protection of the insulator from carbon deposits by creating a suction which appears to remove such deposits. Thelength of time required for such short-circuiting naturally will vary with conditionsfound in a given engine, but in some engines it has been found necessary to clean plugs daily to avoid this, while in some airplane motors even a few hours use of plugs, especially idling while warming up the motor, will toul them. found that such a deflector will part. the stream of gases, directing them outward through the flared holes 32%, away from the insulator, and away from the .re-entrant chamber 11 often formed; at the tip of such insulators, so that. in the same motors such plugs will not require cleaning after days and weeks of use. While this effect is present in the type of plug illustrated in my patent referred to above. I have found that by shielding-the ii'isulator and the larger part oi the chamber from the direct force of the explosion initiated at the spark s.

- 23, and probably also by reason or thesuction ettect in the chamber 25, there is no tendency .t'or'particles of carbon or of. car

concentrated spark is produced, yet the ball.

22 servesto divide and direct out uirdly the gases passing the spark ap and in this way keeps all parts of the plug tree from oil and from carbon deposits, even when placed in engines which pump oil badly. In the form shown in Figure 3, while the ball is omitted thisproduces no material change in the general results. The gases appear either to be compressed within the dead air chamber formed in the upper part of the skirt between the upper parts of the skirt and the insulator 1, and to form thus a cushion which functions in lieu of the ball 22 to directthe gases outwardlythrough the ports 33, the flaring walls 3% of these ports assisting as before to direct these gases in a smooth curve, or the suction of the gases dividing and passing outward through these flared ports creates asuction within the chamber 25, drawing deposits or potential de 'iosit-torming materials away from the projecting insulator.

In Figure 6 the negative electrode 35 has been shown. as directed towards the ball 22, the tip 21 being omitted andithc spark passing through the gap 23 between the ball 22 and the electrode 35. This 'lorin retains the concentration of the spark without diminishing the self-cleaning ei'fect of the gases moving past the ball and through the ports 33, the spark gap in fact being in the current of the gases.

In Figures 4- and 5 the enlargement otthe lower end of the electrode 2 takes the form eta T-shaped head'22, this extending from the lower end of t 1e electrode 2 towards the lower end of the apron 32. The-spark takes place between one or both ends of the enlargement 22' and the skirt 32 itself. It will be noted that the ends of the head 22" are en-unmanned tothe apron 32 in I have the same manner as the ends of the electrodes 35 and 2 in Figure 3,so that the spark atthe gaps 23 jumps -from the edge of the l'OUlKlE end head 22 to the inner edge of the lower end, of the apron 32. lVhile in this form the enlargement 22 serves to some extent to spread and direct the gases past the spark gaps 23 and through. the'ports 33, tea large extent the action in this form correspondsto that, in the term of Figure 3.

One underlying idea in the present invention is the employment of a concentrated spark, between ainegativc and apositive electrode in the form, of two wires, or one oi which is replaced by a ball, or by the skirt itself, the other cooperating therewith to concentratev the spark. The principal iuventive thought herei lies in the combination of-members as just described. servin toproduce'a concentrated spark, with means for directing gases past the spark gap to maintain its elements clean, and to produce a. suction or pressure to maintain the insulator clean, such means including the flared ports inthc apron and either a positive deflector in the form of an enlarged or ball:

shapedl head on the electrode, or perhaps a passive deflector inthe form of the cushion oi dead gas in the upper part ofthe skirt. it departs from the invention ClIlSClOSQt in my previous. patent, referred to above. in that the deflector ball does not cooperate directly with the apron to form an annula spark gap, but. where employed, functions merely a deflector, except as it may cooperate as in Figures l or 6, with a second electrode to form a concentrated spark.

' .Vhat. I claim as my invention is:

1. A spark plug comprising a shell termi-r nating at its lower end in a depending substantially straight-side apron, open at its bottom, an insuator supported in said shell, an electrode extending through said insulator, said apron having a plurality of spaced ports, said electrode havingan cnla'rged head termed thereon materially be low the upper edges of said ports, said ports having outwardly flaring upper edges which, in conjunction with the enlargedhead upon the electrode. direct a current of gases which pass upward through the anniiilar space between the enlarged head and the apron, outwardly in a smooth curve, and a second electrode extending from the shell to the first electrode and cooperating therewith to form a spark gap positioned within the influence of such current of gas to be kept clean thereby.

2. A spark plug as in claim 1. the enlarged head being positioned slightly above the lower end of the f rst electrode, and'said second electrode being. directed toward the projecting tip of the first electrode, 'to' form therewith the spark :gap. and thefenlarged head beingi r e i to deflect; the Current of gases outwardly and upwardly in all direct i a substantially tions from said spark gap. i

'A spark plug comprising a shell termimating at its lower end in a depending substantially straight-side apron, open at its bottom, an insulator supported in saidv shell, and projecting within and spaced therefrom at its lower end to form a chamber above the lower ends of the insulator and apron,

anelectrode extending through said insulator, said apron having a plurality of spaced apertures above 1ts lower end and substantially at the lower end of the insulator, communicating with the lower portion of said c-hainber. the end of saidelectrode being spaced from and cooperating with a complemental member to lorm a spark gap therebetween, said spark gap being positioned materially below the upper edges of said ports, andsaid upper edges being flared upwardly and outwardly,

whereby gases passing the spark gap will be directed outwardly through saidports 1n smoothly curved path, whereby a current of gas is induced through the open end'of the apron, and past the spark gap, to produce suction therein tending to maintain all elements within the influence of said gas current clean' 4. In. a spark plug of the type comprising a substantially straight-sided shell freely open at its lower end and having upwardly and outwardly flared apertures thereaboye' and thereab'out, an insulator projecting within the lower end ofsaid shell and spaced therefrom, and. an electrode held in said insulator and projecting therebelow and terminating substantially at the lower end of said shell, a deflector on the projecting portion of said electrode, the lower surface of said deflector bein located below said flared apertures and being curved to cooperate therewith to cause and directout wardly in a smooth curve an upward current of gases entering the open end of said shell,

and asecond electrode cooperating with said first electrode to form a spark gap located within the influence of sald current of gases to be maintained clean thereby, and so located, with respect to the deflector, that the interior of said shell is largely shielded by the deflector from the direct force of thee e plosion initiated at said spark gap.

5. In a spark plug of thetype comprising a substantially straight-sided shell freely open at its lower end and having upwardly and outwardly flared apertures thereabore and thereabout, an insulator'projecting with in the lower end otsaid shell and spaced therefrom, and an electrode held in said insulatorand projecting therebelow to position itstip substantially at the lower end Oi said shell, a deflector on theprojecting por 7 tion of said electrode, the lower surface of said deflector being located below said flared apertures and being curved to cooperate therewith to cause and direct outwardly in a smooth curve'anupward current of gases entering the open end of said shell, the

MAYNARD r. MACDONALD. 

